The present invention relates to a photosensitive body for electrophotography (henceforth may also be referred to as simply xe2x80x9cphotosensitive bodyxe2x80x9d) and to an electrophotography device equipped with this electrophotography photosensitive body.
In recent years, in the field of electrophotography photosensitive bodies, many of what are called organic electrophotography photosensitive bodies, which use organic photoconductive materials, have been proposed and implemented. These are non-polluting and have low cost, and because there is a large degree of freedom in the choice of materials, they can be designed to have varied photosensitive body properties.
The photosensitive layer of an organic electrophotography photosensitive body comprises mainly a layer in which organic photoconductive materials are dispersed in a resin. Many laminated constructions and single layer constructions have been proposed. In a laminated construction, a layer in which a charge generating substance is dispersed in a resin and a layer in which a charge transport substance is dispersed in a resin are layered. A single-layer construction comprises a single layer in which a charge generating substance and a charge transport substance are dispersed in a resin.
Among these, a photosensitive body using a function-separated model for the construction of the photosensitive layer has been widely implemented because of its excellent photosensitive body properties and durability. A function-separated model has a charge transport layer laminated on top of a charge generating layer. In this function-separated laminated photosensitive body, a hole transport material is mainly used for the charge transport layer. As a result, they are generally used with a negative charging process. Negative corona charging used in the negative charging process is unstable compared to positive corona charging, and the amount of generated ozone is also large. As a result, there are problems of having a negative impact on the photosensitive body and a negative impact on the usage environment.
For solving these problems, an organic electrophotography photosensitive body that can use a positive charging is effective. As a result, currently there is a demand for a positive charge photosensitive body with high sensitivity. For this positive charge photosensitive body, there have been many proposals for a function-separated photosensitive body or a single-layer photosensitive body. The function-separated photosensitive body has a photosensitive layer in which a charge generating layer is layered on top of a hole transport layer or a photosensitive layer in which an electron transport layer is layered on top of a charge generating layer. A single layer photosensitive body has a photosensitive layer containing a charge generating substance and a charge transporting substance in a single layer.
In recent years, in Japanese Laid Open Patent Publication Number 1-206349, Japanese Laid Open Patent Publication number 4-360148, Denshishashin Gakkaishi (Electrophotography Society Journal) Vol. 30, p. 266xcx9c273 (1991), Japanese Laid-Open Patent Publication Number 3-290666, Japanese Laid Open Patent Publication Number 5-92936, Pan-Pacific Imaging Conference/Japan Hardcopy ""98 Jul. 15-17, 1998 J A HALL, Tokyo, Japan, preliminary draft collection p. 207-210, Japanese Laid-Open Patent Publication Number 9-151157, Japan Hardcopy ""97 Collection of papers Jul. 9, 10, 11, 1997 J A Hall (Tokyo-Ohtemachi) p.21-24, Japanese Laid Open Patent Publication Number 5-279582, Japanese Laid Open Patent Publication Number 7-179775, Japan Hardcopy ""92 collection of papers Jul. 6, 7, 8, 1992 J A Hall (Tokyo-Ohtemachi) p. 173-176, Japanese Laid Open Patent Publication Number 10-73937, and the like, many electron transport substances and electrophotography photosensitive bodies using these electron transport substances have been proposed and described, and there has been much interest in them. Furthermore, as described in Japanese Laid Open Patent Publication Number 5-150481, Japanese Laid Open Patent Publication Number 6-130688, Japanese Laid-Open patent Publication Number 9-281728, Japanese Laid-Open patent Publication Number 9-281729, Japanese Laid-Open Patent Publication number 10-239874, a photosensitive body using a combination of a hole transport substance and an electron transport substance in a single layer photosensitive layer has been attracting attention as having high sensitivity, and this has been implemented by some. However, with the positive charge photosensitive body, the electrical properties of sensitivity and the like are still deficient compared to the negative charge function-separated photosensitive body.
Furthermore, for the charge generating substance, various studies have been conducted from the prior art. In general, for the charge generating substance, various pigments are used according to the sensitivity range of the photosensitive body. In particular, for photosensitive bodies responding to light of semiconductor laser light or infrared LED light and the like which have wavelengths in the infrared or near-infrared region, phthalocyanine pigments such as metal free phthalocyanine, titanyl phthalocyanine, and the like are widely used. There are various crystal types for these phthalocyanine pigments. It is known that the wavelength region and quantum efficiency of the absorbed light are different depending on the different crystal types, and for the electrophotography photosensitive body using these pigments as a charge generating substance, the different crystal types also affect the sensitivity and electrical properties such as the residual voltage, dark attenuation, as well as the stability of the photosensitive body over repeated use, and the like. Various studies have been conducted on the relationship between the crystal type and the photosensitive body electrical properties.
For example, in Japanese Laid Open Patent Publication Number 61-217050, there is proposed a single layer photosensitive body having a photosensitive layer comprising an alpha titanyl phthalocyanine dispersed in a binding resin. In an X ray diffraction spectrum having CuK alpha as the radiation source, this alpha titanyl phthalocyanine shows strong diffraction peaks at Bragg angles (2xcex8xc2x10.2 degrees) of 7.5, 12.3, 16.3, 25.3, and 28.7 degrees.
In addition in Japanese Laid Open Patent Publication Number 9-73182, there is proposed an electrophotography photosensitive body that is a single layer photosensitive body containing a charge transport substance and a charge generating substance in a photosensitive layer. The charge generating substance comprises, in an x-ray diffraction spectrum as described above, a mixture of a metal free phthalocyanine showing diffraction peaks at Bragg angles (2xcex8xc2x10.2 degrees) of 7.5, 9.1, 16.7, 17.4, 22.3, and 28.6 degrees and a titanyl phthalocyanine showing diffraction peaks at Bragg angles (2xcex8xc2x10.2 degrees) of 9.5, 14.2, 24.0, and 27.2 degrees. The content ratio of the titanyl phthalocyanine to the total weight of the charge generating substance is greater than 50 weight %.
However, even with these numerous single layer electrophotography photosensitive bodies that have been proposed, the electrical properties of sensitivity and the like are not adequate compared to the function-separated photosensitive body of negative charge of the prior art. Photosensitive bodies that can use positive charge and that have good electrical properties have still not been satisfactorily achieved.
It is an object of the present invention to provide an electrophotography photosensitive body which solves the above problems.
It is a further object of the present invention to provide an electrophotography photosensitive body and an electrophotography device equipped with the same, in which for an electrophotography photosensitive body having a single layer photosensitive layer, the electrical properties with positive charging are excellent and there is excellent stability over repeated use.
As a result of intensive study in order to solve the above object, the present inventors have discovered the following. With an electrophotography photosensitive body having a single layer photosensitive layer containing at least a resin binder, a charge generating substance and a charge transport substance, by using as a charge generating substance a titanyl phthalocyanine with a crystallinity equal to or less than a constant value, the electrical properties with positive charging, such as the sensitivity, the residual electric potential, and dark attenuation, were improved, and the present invention was completed.
In other words, the present invention is an electrophotography photosensitive body, having a single layer photosensitive layer on top of a conductive substrate directly or via an undercoat layer, and the single layer photosensitive layer containing at least a resin binder, a charge generating substance, and a charge transport substance, wherein: at least one of the charge generating substances is a titanyl phthalocyanine; with the titanyl phthalocyanine, in a x-ray powder diffraction spectrum having a radiation source of CuK alpha and within a range of a Bragg angle 2xcex8xc2x15xcx9c35 degrees, a ratio R (henceforth referred to as xe2x80x9ccrystallinityxe2x80x9d) of a value P of a diffraction intensity of a highest peak and a value B of a background diffraction intensity satisfies a following equation
R=(Pxe2x88x92B)/B less than =7.0,
and preferably satisfies a following equation
R=(Pxe2x88x92B)/B less than =3.0
wherein P is a value of a diffraction intensity of a highest peak. At a same Bragg angle as the highest peak, B is a value of a diffraction intensity of a line that connects the troughs on either side of the highest peak.
In the present invention, the charge transport substance can be a hole transport substance. In addition, it can also include both a hole transport substance and an electron transport substance.
In addition, at least one type of the hole transport substance is preferably a compound having a construction represented by one of the following general formulas (HT1)xcx9c(HT4). 
In formula (HT1), RH1xcx9cRH32 are each independently a hydrogen atom, a C1-C6 alkyl group, or a C1-C6 alkoxy group with a carbon number of 1xcx9c6. 
In formula (HT2), RH33 represents a hydrogen atom or a C1-C6 alkyl group. RH34 and RH35 each independently represent a hydrogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, or an optionally substituted aryl group, and they can form a ring by directly bonding or bonding via an oxygen atom, sulfur atom, or a carbon chain. RH36 and RH37 each independently represent a C1-C6 alkyl group, an optionally substituted C3-C12 cycloalkyl group, an optionally substituted aryl group, or an optionally substituted aralkyl group. RH38xcx9cRH41 each independently represent a hydrogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, or an optionally substituted aryl group. Of RH36xcx9cRH41, two or more of the groups can be bonded directly or via an oxygen atom, sulfur atom, or carbon chain to form a ring. m represents 0 or 1. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, an optionally substituted aryl group, an optionally substituted aryl alkoxy group, a hydroxyl group, a cyano group, an amino group, a nitro group, a halogenated alkyl group, an alkyl substituted amino group, or an aryl substituted amino group. Of the substitution groups, two or more of the groups can be bonded directly or bonded via an oxygen atom, sulfur atom, or carbon chain to form a ring. 
In formula (HT3), RH42xcx9cRH60 each independently represent a hydrogen atom, a halogen atom, a C1-C12 alkyl group, a C1-C12 alkoxy group, an alkyl substituted amino group, or an optionally substituted aryl group. Of these, two or more groups can be bonded directly or via an oxygen atom, sulfur atom, or a carbon chain to form a ring. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. Of the substitution groups, two or more of the groups can be bonded directly or via an oxygen atom, a sulfur atom, or a carbon chain to form a ring. 
In formula (HT4), RH61xcx9cRH88 each independently represent hydrogen atom, a halogen atom, a C1-C12 alkyl group, a C1-C12 alkoxy group, or an optionally substituted aryl group. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, or an aryl group.
Furthermore, at least one type of the electron transport substance is preferably a compound having a construction represented by one of the following general formulas (ET1)xcx9c(ET4). 
In formula (ET1), RE1xcx9cRE4 each independently represent a hydrogen atom, a C1-C12 alkyl group, a C1-C12 alkoxy group, an optionally substituted aryl group, a cycloalkyl group, an optionally substituted aralkyl group, or a halogenated alkyl group. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. 
In formula (ET2), RE51 xcx9cRE8 each independently represent a hydrogen atom, a C1-C12 alkyl group, a C1-C12 alkoxy group, an optionally substituted aryl group, a cycloalkyl group, an optionally substituted aralkyl group, or a halogenated alkyl group. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. 
In formula (ET3), RE9 and RE10 each independently represent a hydrogen atom, a C1-C12 alkyl group, a C1-C12 alkoxy group, an optionally substituted aryl group, a cycloalkyl group, an optionally substituted aralkyl group, or a halogenated alkyl group. RE11 represents a hydrogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, an optionally substituted aryl group, a cycloalkyl group, an optionally substituted aralkyl group, or a halogenated alkyl group. RE12xcx9cRE16 each independently represent a hydrogen atom, a halogen atom, a C1-C12 alkyl group, a C1-C12 alkoxy group, an optionally substituted aryl group, an optionally substituted aralkyl group, an optionally substituted phenoxy group, a halogenated alkyl group, a cyano group, or a nitro group. Of these, two or more of the groups can be bonded to form a ring. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C12 alkoxy group, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. 
In formula (ET4), RE17 represents an optionally substituted alkyl group or an optionally substituted aryl group. RE18 represents an optionally substituted alkyl group, an optionally substituted aryl group, or a group represented by a following formula (ET4a),
xe2x80x94Oxe2x80x94RE19xe2x80x83xe2x80x83(ET4a)
wherein, RE19 represents an optionally substituted alkyl group or an optionally substituted aryl group. The substitution group represents a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, an aryl group, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group.
Furthermore, at least one type of the resin binder is a polycarbonate having a construction unit represented by a following general formula (BD1) as a main repeating unit, 
wherein RB1xcx9cRB8 each independently represent a hydrogen atom, a C1-C6 alkyl group, an optionally substituted aryl group, a cycloalkyl group or a halogen atom. Z represents an atomic group that is necessary to form an optionally substituted carbon ring. The substitution group represents a C1-C6 alkyl group, an aryl group, or a halogen atom.
In addition, the electrophotography device of the present invention is equipped with an electrophotography photosensitive body of the present invention as described above. In addition, the charging process is conducted by a positive charging process.
The above, and other objects, features, and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.